Two men forced their way into the bank and demanded cash before leaving the premises shortly afterwards with a substantial amount of money.
The men got into a silver Ford Focus which was waiting outside.
The vehicle drove off through a car park before being abandoned near to a supermarket on Welford Road, Blaby.
Three men wearing caps and dark hooded clothing got into another car which drove off at speed along Welford Road in the direction of Countesthorpe.
Detective Sergeant Simon Head, the investigating officer, said:
“The staff were inside the locked bank when the incident happened and although left shaken fortunately nobody was hurt.
“We are carrying out extensive enquiries to locate those responsible and would ask that anyone who saw either of the vehicles being driven, the incident itself taking place or know who was responsible to contact police.”
Anyone with any information in relation to this incident call 101.